Agronomists say you shouldn't plant corn until the soil temperature is 50 degrees F at the 4-inch depth. How important is that number when you look at the calendar and see it's the 15th of April?
Related: When to plant corn in central Midwest
"That's kind of a magic number, 50 degrees, for planting corn," observes Jim Fawcett, an Iowa State University Extension field agronomist in eastern Iowa. "That's when corn will germinate, with a soil temperature of 50 degrees or higher.
"The reason for not planting before that is the seed actually will take up water with soil temperatures cooler than 50 degrees. The seed will swell, but it doesn't germinate. That's not a good combination because the seed will tend to rot if it's just sitting there swelling in the soil but not germinating. The seed imbibes the water, takes it in, but doesn't germinate because it's too cold."
Fawcett adds, "Particularly in April, I would definitely be paying attention to soil temperature before I decide to plant corn."
As for timeline, the ideal corn planting window is April 20 to May 5 in Iowa. "A lot of farmers have big planters and enough help that they can get their corn acreage planted in 3 to 5 days. If you can do that, there's no sense in trying to push things along before soil conditions are right," Fawcett says.
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